As the commercial significance of the Internet increases, business-to-consumer (“B2C”), business-to-business (“B2B”), and other electronic marketplaces have become increasingly prevalent. Each marketplace typically requires a different set of software applications to provide the capabilities that users of the marketplace expect, some being common to many marketplaces and some being customized to particular marketplaces. Previous techniques for developing such applications have required each application to be developed essentially from scratch, requiring extensive programming resources for defining the particular way in which it handles data, the particular rules that control its operation, and the particular communications between it and other applications or other external systems. This makes development of electronic marketplaces relatively slow and expensive. The applications must typically be tightly coupled to one another, which not only makes it difficult to modify applications, but leads to performance penalties in addition. As a result of the time and expense associated with creating and modifying electronic marketplaces, companies that develop such marketplaces for their customers are typically forced to use a “one size fits all” approach to marketplace development, with little if any variation between customers. This lack of customization may often lead to poorer customer satisfaction and other negative consequences. Any of these or other deficiencies have made previous techniques for developing applications, such as those associated with electronic marketplaces, inadequate for many needs.